1. Field of the Invention
The invention pertains to an electronic push button or push button assembly for use as a call or signal generator, particularly in elevator controls, for installation, with rear surface attachment, in a service control station or indicator board on floors and in elevator cars including a push button guide, carrier plate, means for optical acceptance or acknowledgement, and an electronic portion.
2. Discussion of the Background of the Invention and Material Information
Push buttons of the aforementioned type are known in different variations, on one hand with reference to the utilized active elements and, on the other hand, with reference to the constructional shape or development. The phrase "active element" denotes such structural details, which produce an electrical signal as a result of a mechanical force input or which at least changes its electrical characteristics. Structural details of the first type are, for example, those which function according to the piezo-electric principle. Upon a force input the piezo-electric crystal gives off a voltage pulse. Structural details of the second type, upon force input, change their electrical properties in the sense that, for example, the capacity values, the inductance, or the ohmic resistance undergoes a change in value.
It is known that such elements are utilized in the construction of silent or click-free switches. In addition, a further advantage is utilized in that push buttons with extremely short or no actuation travel or stroke can be realized.
U.S. Pat. No. 4,805,739 describes a push button element for elevator control stations or indicator boards which function according to the piezo-electric principle. Without an ascertainable mechanical actuation path, upon pressing of a membrane-like disk, a piezo-electric element, attached to the rear surface of this disk, is actuated and the voltage pulse resulting therefrom is utilized as a control signal. A transparent housing, transfers the acknowledgement or "call-registered" signal via LED's to an illuminated ring on the surface of the control station or indicator board.
Operating personnel deem it a deficiency if the switch actuation does not involve an actuation path or movement.
Further U.S. Pat. No. 4,489,302 describes an element that changes electrically as a result of force or pressure. It pertains to a multi-layer semi-conductor element, which, independent of an actuation path, changes its electrical resistance. A constructive embodiment for a useful or practical push button element is not presented.
Published German Patent Application DE 37 03 666 discloses the use of a pressure dependent resistance for a call emitter or calling device having a LED-acceptance or acknowledgement. The illustrated solution for such a push button element in FIG. 3 is, however, only symbolic and is not a valid useable construction.